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commandlinefu.com is the place to record those command-line gems that you return to again and again.

Delete that bloated snippets file you've been using and share your personal repository with the world.
That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and
voted up or down.

Stay in the loop…

Follow the Tweets.

Every new command is wrapped in a tweet and posted
to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning,
there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.

Execute commands serially on a list of hosts. Each ssh connection is made in the background so that if, after five seconds, it hasn't closed, it will be killed and the script will go on to the next system.

Using the output of 'ps' to determine CPU usage is misleading, as the CPU column in 'ps' shows CPU usage per process over the entire lifetime of the process. In order to get *current* CPU usage (without scraping a top screen) you need to pull some numbers from /proc/stat. Here, we take two readings, once second apart, determine how much IDLE time was spent across all CPUs, divide by the number of CPUs, and then subtract from 100 to get non-idle time.

In this example, the command will recursively find files (-type f) under /some/path, where the path ends in .mp3, case insensitive (-iregex).

It will then output a single line of output (-print0), with results terminated by a the null character (octal 000). Suitable for piping to xargs -0. This type of output avoids issues with garbage in paths, like unclosed quotes.

The tr command then strips away everything but the null chars, finally piping to wc -c, to get a character count.

I have found this very useful, to verify one is getting the right number of before you actually process the results through xargs or similar. Yes, one can issue the find without the -print0 and use wc -l, however if you want to be 1000% sure your find command is giving you the expected number of results, this is a simple way to check.

The approach can be made in to a function and then included in .bashrc or similar. e.g.

count_chars() { tr -d -c "$1" | wc -c; }

In this form it provides a versatile character counter of text streams :)